Metering pump with self-calibration and health prediction

• US 20070196213A1
• Filed: 02/22/2006
• Published: 08/23/2007
• Est. Priority Date: 02/22/2006
• Status: Active Grant

• Current Assignee: Hamilton Sundstrand Corporation (Rtx Corporation)
• Original Assignee: Hamilton Sundstrand Corporation (Rtx Corporation)
• Inventors: Parsons, Douglas, Alstrin, Kevin
• Granted Patent: US 7,798,781 B2
• Time in Patent Office: Days
• US Class Current: 417/32
• CPC Class Codes: F04B 2201/0803 Leakage
• CPC Class Codes: F04B 2203/0201 Current
• CPC Class Codes: F04B 2203/0209 Rotational speed
• CPC Class Codes: F04B 49/065 and making use of computers
• CPC Class Codes: F04B 51/00 Testing machines, pumps, or pumping installations
• CPC Class Codes: F04C 14/08 characterised by varying the rotational speed
• CPC Class Codes: F04C 2220/24 for metering throughflow
• CPC Class Codes: F04C 2240/81 Sensor, e.g. electronic sensor for control or monitoring
• CPC Class Codes: F04C 2270/80 Diagnostics
• CPC Class Codes: F04C 2270/86 Detection

Abstract

A metering pump incorporates a method of relating inner loop current to a pump output pressure. Pump/motor speed, which correlates to current, is measured and controlled by a system controller. System temperature is also measured by the system controller. The controller monitors the measured system temperature and provides for compensation for system losses, including inductive-resistive (IR) losses, and for density and viscosity shifts, within a pre-determined allowable system temperature operating range. An initial system calibration is conducted using a “shut-off” test, where the metering pump is run at a very slow known speed while the system is shut-off. After initial start-up, a health-monitoring feature continues to monitor the current as an indicator of pump performance and continuously adjusts a motor speed to maintain a desired level of pump performance. This provides the system with the ability to compensate for performance losses, including performance losses due to variations in operating conditions, and to compensate for pump wear.

Claims

1. A method of controlling a pumping system comprising the steps of:

(a) selecting a first system operating characteristic;

(b) selecting a system health factor;

(c) determining a system operating function level based upon a relationship between the first system operating characteristic and the system health factor;

(d) comparing the system operating function level to a desired system operating function level; and

(e) adjusting a second system operating characteristic to achieve the desired system operating function level if the system operating function level is different than the desired system operating function level.

2. The method of claim 1, further including the step of determining a nominal value relationship between the first system operating characteristic and the system health factor.

3. The method of claim 2, further including measuring pump leakage by running a pump while the pumping system is off and adjusting the nominal value relationship based upon a measured pump leakage.

4. The method of claim 2, further including the step of determining a nominal value relationship range based upon the nominal value relationship and a pre-determined system operating temperature range.

5. The method of claim 1, further including the steps of measuring a system temperature, measuring the first system operating characteristic, measuring the second system operating characteristic and repeating step (c) through step (e).

6. The method of claim 5, wherein at least one of the first system operating characteristic and the second system operating characteristic is measured by direct measurement.

7. The method of claim 5, wherein at least one of the first system operating characteristic and the second system operating characteristic is measured based upon feedback generated by a motor.

8. The method of claim 1, wherein the first system operating characteristic is a system current.

9. The method of claim 8, wherein the system current is a root mean square current.

10. The method of claim 8, wherein the system current is a phase current.

11. The method of claim 1, wherein the second system operating characteristic is a motor speed.

12. The method of claim 1, further including continuously repeating step (b) through step (e).

13. The method of claim 1, wherein the first system operating characteristic is a system current, the second system operating characteristic is a motor speed, the system health factor is pump leakage, and the desired system operating function level is normal system function.

14. The method of claim 13, wherein step (e) further includes decreasing the motor speed based upon a nominal value relationship when a measured system temperature falls outside a pre-determined system operating temperature range and the system current exceeds a maximum value associated with the normal system function level.

15. The method of claim 13, wherein step (e) further includes increasing the motor speed based upon a nominal value relationship when a measured system temperature falls outside a pre-determined system operating temperature range and the system current falls below a minimum value associated with the normal system function level.

16. A demand flow system comprising:

a motor;

a pump driven by the motor; and

a controller that determines a baseline system operating function level associated with a baseline flow of the pump, compares the baseline system operating function level to a desired system operating function level associated with a desired flow of the pump, initially adjusts at least one system operating characteristic to achieve the desired system operating function level if the baseline system operating function level is different than the desired system operating function level, monitors an actual system operating function level during system use, and continues to adjust the system operating characteristic to maintain the actual system operating function level at the desired system operating function level.

17. The demand flow system of claim 16, wherein the baseline system operating function level is determined based upon a relationship between at least one measured system characteristic and a system health factor.

18. The demand flow system of claim 17, wherein the at least one measured system characteristic comprises a system current and a system operating temperature, and wherein the at least one system operating characteristic comprises motor speed.

19. The demand flow system of claim 18, wherein the controller decreases motor speed when a measured system operating temperature falls outside a pre-determined system operating temperature range and a measured system current is greater than a pre-determined maximum current.

20. The demand flow system of claim 18, wherein the controller increases motor speed when a measured system operating temperature falls outside a pre-determined system operating temperature range and a measured system current is less than a pre-determined minimum current.